The invention pertains to computer input devices used for cursor or pointer control on a video display. More particularly, the invention pertains to a cursor control device which provides input based upon on its orientation as distinguished from its position.
There are a variety of computer cursor control devices presently on the market. Although the position of a cursor on a computer display may be controlled by use of keys on a keyboard (such as the standard four directional arrow keys), an accessory device is often used instead.
The most common such device is a "mouse." The mouse is typically moved over a planar surface such as a table top to provide two dimensional cursor control information to the computer responsive to movement within the plane. The most common type of mouse is the ball-type mouse. One such mouse is disclosed in U.S. Pat. No. 4,464,652 by William F. Lapson and William D. Atkinson, the disclosure of which is incorporated herein by reference. In such a mouse, a uniform spherical ball is suspended within a housing and is exposed at the base of the housing so as to contact any planar surface upon which the mouse is placed. As the user grips the housing and moves the mouse over the surface, the ball rolls. As the ball rolls, its orientation relative to the housing changes. A pair of orthogonal encoders detect the change in relative orientation and provide a corresponding input to the computer.
In a typical mouse, the switches and encoders or transducers provide raw signal information to circuitry within the mouse. The signals are processed and combined by circuitry in the mouse into a form suitable for communication as output signals from the mouse to the computer. Thereafter the signals are processed by software in the computer, typically designated as a mouse driver, and then used to provide input to another software program. Exemplary signal, hardware and software protocols are disclosed in THE WINN ROSCH HARDWARE BIBLE, Simon & Schuster, Inc. 1989, ISBN 0-13-160979-3 (See pp. 256-264); GUIDE TO THE MACINTOSH FAMILY HARDWARE, Addison-Wesley Publishing Company, Inc. 1990, ISBN 0-201-52405-8; and LOGITECH MOUSE USER'S MANUAL, Logitech, Inc. 1988, the disclosures of which are incorporated herein by reference. In a two-button protocol used by Microsoft Corporation and a three-button protocol used by MSC Technologies, Inc., information is communicated from the mouse to the computer in respective three and five-byte groups wherein, respectively, two and three bits of the first byte in the group correspond to the state of each button (more particularly to the state of the switch associated with each button).
In many such mice, the ball is held within the housing by an annular retainer clip (or lock cap) which is secured to the base of the housing by a bayonet or similar type fitting. The ball projects through the central opening in the retainer clip for engaging the surface upon which the mouse is placed. To remove the ball, such as for cleaning, the clip is rotated so as to disengage its fitting and is then extracted, permitting the ball to be removed from the housing.